1. Field of the Invention
The present invention relates to a slide switch to be used in an attached state to, for example, a case of an electronic device for an automobile. Particularly, the invention is concerned with a waterproof structure for both the case and an operating knob.
2. Description of the Prior Art
As an electronic device used in an automobile there is known a remote keyless entry device, in which is used a slide switch as a memory recall switch.
An example of such a conventional slide switch is illustrated in FIGS. 6 to 10, of which FIG. 6 is an exploded perspective view of a remote keyless entry device, FIG. 7 is an exploded perspective view of a slide switch portion, FIG. 8 is a plan view of the slide switch portion, FIG. 9 is a sectional view taken on line 9--9 in FIG. 8, and FIG. 10 is a sectional view taken on line 10--10 in FIG. 8.
In the figures, an upper case 11 and a lower case 12 are each formed in a box shape having a receptacle portion in the interior thereof, using an insulating material such as a synthetic resin. The upper and lower cases 11, 12 are superimposed one on the other to constitute a casing. A plurality of window apertures 11a are formed in the upper case 11 and a rubber key pad 13 is received in the receptacle portion of the case. The rubber key pad 13 is formed in a box shape having a lower opening, using, for example, silicone rubber or an elastomer resin having flexibility. On an upper surface side of the rubber key pad 13 are integrally formed a plurality of operating keys 13a so as to project into the window apertures 11a respectively. Further, a substrate block 15 with electronic circuit components, e.g., push-button switches 14, mounted thereon is attached to a lower surface side of the rubber key pad 13. Thus, the substrate block 15 is covered with the rubber key pad 13 to shield the electronic circuit components against the entry of water or water drops.
The lower case 12 is provided with a cell receptacle portion 12a for receiving a button-shaped cell 16 therein and is also provided with a contact receptacle portion 12b for receiving therein a slide contact 17 as a contact member which constitutes a slide switch. The slide contact 17 is formed using an electrically conductive metallic plate such as, for example, a stainless steel plate or a phosphor bronze plate. The slide contact 17 is disposed in the contact receptacle portion 12b slidably. Further, the slide contact 17 is provided with spring pieces 17a for elastic contact with the inside of the lower case 12. Outside the lower case 12 is mounted a slide knob 18 which is engaged with the slide contact 17 and which is formed of an insulating material such as a synthetic resin, and is also provided a slide portion 12c adapted to be slid. The slide portion 12c is formed with a slide hole 12d for insertion therein of a shaft portion 18a of the slide knob 18.
Outside the slide hole 12d of the slide portion 12c is formed an annular recess 12e, into which is engaged an O ring-like rubber seal 19 formed of an elastic material such as rubber. When the shaft portion 18a of the slide knob 18 is inserted into the slide hole 12d of the lower case 12 and is put in engagement with the slide contact 17, a lower surface of the slide knob 18 is brought into elastic contact with the rubber seal 19 with the biasing force of the spring pieces 17a of the slide contact 17, thereby preventing the entry of water or water drops from the slide hole 12d of the slide portion 12c.
However, in the above conventional slide switch structure, for stably positioning the O ring-like rubber seal 19 against a frictional force acting between it and a lower surface of the slide knob 18, it is necessary that the recess 12e be formed in the slide portion 12c and that therefore the thickness of the lower case 12 be increased by an amount corresponding to the recess 12e, thus giving rise to the problem that the thickness of the casing increases.
Besides, the working efficiency of the work for bringing the rubber seal 19 into engagement with the recess 12c is poor and there arises the problem that the rubber seal 19 comes off during the assembling work.